1. Field of the Invention
The present invention relates to a novel chain polymeric liquid crystal compound, a chain polymeric liquid crystal copolymer compound, each of which has a fluoro group in a flexible spacer portion thereof, their chain polymeric liquid crystal compound, a polymeric liquid crystal composition containing the chain polymeric liquid crystal copolymer compound, their chain polymeric liquid crystal compound, a polymeric liquid crystal device which uses the chain polymeric liquid crystal copolymer compound or the polymeric liquid crystal composition, and an apparatus and a method which use the same.
The chain polymeric liquid crystal compound, the chain polymeric liquid crystal copolymer compound and the polymeric liquid crystal composition according to the present invention can be used as optoelectronic material and optical equipment material and the like represented by a display and a memory.
2. Description of the Prior Art
There has been known a conventional liquid crystal device which uses twisted nematic liquid crystals disclosed in "Voltage Dependent Optical Activity of a Twisted Nematic Liquid Crystal" written by M. Schadt and W. Helfrich, pp. 127 to 128, No. 4, Vol. 18 of Applied Physics Letters (Feb. 15, 1971). However, the aforesaid TN liquid crystal encounters a problem in that crosstalk is generated during a time-division operation in which a matrix electrode structure, in which the pixel density is high, is employed. Therefore, a limit exists on the number of the pixels.
What is even worse, the electric field response is unsatisfactory and the characteristic of angle of visibility is insufficient. Therefore, the use of TN liquid crystals as a display has been limited. Furthermore, since a manufacturing process for forming a thin film transistor in each pixel is too complicated, it is very difficult to manufacture a display device having a large area.
In order to overcome the aforesaid problems experienced with the conventional liquid crystal device, use of a liquid crystal device having bistability has been suggested by Clark and Lagerwall (refer to Japanese Patent Laid-Open No. 56-107216 and the specification of U.S. Pat. No. 4,367,924 and the like).
As the bistable liquid crystal, a ferroelectric liquid crystal composed of chiral smectic phase-C (Sm*C) or phase-H (Sm*H) has been usually employed. The ferroelectric liquid crystal enables a very high response speed to be realized, and as well, bistability having a memory characteristic can be realized because of its spontaneous polarization. Furthermore, an excellent visible angle characteristic can be realized. Therefore, it is considered to be a preferable material for a display having large capacity and large area. However, there arises a technical problem in a case where a liquid crystal cell is formed in that a large area display device cannot easily be manufactured because it is difficult to make a large area which will be monodomain.
A structure has been known in which a polymeric liquid crystal is used as a memory medium.
For example, a heat writing memory is known which has been disclosed in "Thermotropic Liquid Crystalline Polymers. 14", pp. 364 to 365, Vol. 24 of Polymer Communications written by V. Shibaev, S. Kostromin, N. Pla'te, S. Ivaov, V. Vestrov, and I. Yakovlev.
However, the polymeric liquid crystal compound suffers from its insufficiently high glass transition point realized in a case where the memory medium having the polymeric liquid crystal is used to store recorded data by utilizing its glass transition point. Another problem arises in that the response speed is unsatisfactorily lowered due to the polymerizing process. Therefore, it has not been put to practical use.
Furthermore, a side chain type ferroelectric polymeric liquid crystal has been disclosed in Japanese Patent Laid-Open No. 63-72784 (see counterpart U.S. Pat. Nos. 4,844,835 and 4,913,839), Japanese Patent Laid-Open No. 63-99204 (same U.S. counterparts) and Japanese Patent Laid-Open No. 63-161005. However, the side chain type polymeric liquid crystal encounters a problem in that a uniform orientation cannot easily be realized by the stretching orientation which is the simplest orientation means.
On the other hand, a chain ferroelectric polymeric liquid crystal having a hydrocarbon type chiral diol has been reported in polymer Preprints, Japan, Vol. 38, No. 8, p.p. 2371 to 2373 (1989) by a group including Watanabe. However, a satisfactorily large spontaneous polarization cannot be obtained and thereby the realized response speed is too low because a hydrocarbon chiral diol is used as the chiral group.